Impression post and temporary abutment and method of making dental restoration

ABSTRACT

The disclosed fixture mount limits torque that may be applied when installing a dental implant and also serves as an impression post and an abutment for a temporary prosthesis. In preferred embodiments, the fixture mount is formed of plastic and is subject to chair side modifications by the surgeon so as to be better suited as an abutment. Methods of shaping the fixture mount for use as an abutment and for making a dental restoration using the shaped abutment are disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of priority of U.S. ProvisionalApplication Serial No. 60/322,620, filed Sep. 26, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates generally to the field of dentalimplantogy. More specifically, the invention relates to apparatus andmethods allowing chair-side modifications to be made to components usedin making dental restorations.

[0004] 2. Background Information

[0005] Dental implants play an extraordinarily important role in moderndentistry. Implants serve as the foundation for a variety of dentalprostheses as may be provided to correct debilitating or embarrassingconditions caused by, for example, disease, accident or natural aging.

[0006] In order to adequately support the dental prosthesis for which itis intended, the implant (also referred to as a “fixture”) is surgicallyimplanted into healthy bone tissue of the patient's alveolar (jaw) bone.To install the implant, the surgical site is prepared by first incisingthe gingival tissue at the implant site and then drilling a generallycylindrical bore into the bone mass. The prepared bore is referred as anosteotomy. Although implants may be made in a variety of forms, aconventional and a very common implant has a generally cylindrical bodythat is externally threaded and tapered at one end. The taper may extendfor only the distance of the first few threads or extend for nearly theentire length of the implant. In recent years, it has becomeconventional to apply certain coatings to the outer surfaces of theimplants. These coatings, such as hydroxyapatite (HA) or Titanium PlasmaSpray (TPS), enable the bone tissue to better integrate with theimplant, thereby providing enhanced support for the prosthesis.

[0007] Once the osteotomy is prepared, the tapered end of the implant ispositioned in the osteotomy, and a powered or manual driving tool isemployed by the surgeon to rotate the implant and drive it into theosteotomy, which may or may not have been pre-threaded or tapped toreceive the implant. The driving tool includes an end portion that isconfigured to matingly engage the end of the implant so as to transmittorque to the implant.

[0008] In some instances, both to deliver the implant to the surgicalsite and to drive the implant into the osteotomy, a piece referred to asa “fixture mount” is attached to the top of the implant by a retainingscrew and it, rather than the implant, directly engages the drivingtool. In this manner, the fixture mount serves as an intermediate memberfor transmitting to the implant the torque applied by the driving tool.Conventional fixture mounts have been made of metal, such as titanium.

[0009] The size of the osteotomy and the density of the bone mass at thesurgical site will dictate the amount of torque that must be applied tothe implant during installation. For example, where the bone density isgreater than anticipated, the dental surgeon may find that an unusuallyhigh torque is required in order to implant the device. Presently, ifthe surgeon believes, based on tactile feedback, that the implant isexperiencing excessive resistive force, such that a potentially damagingtorque would have to be applied in order to install the implant, thesurgeon must extract the then partially-installed implant. Typically,this is accomplished by reversing the drive tool's direction ofrotation, and using the drive tool and fixture mount to “back-out” theimplant from the osteotomy, which can then be widened with a largerdrill or tapped as necessary.

[0010] If this procedure is not followed and, instead, an excessivetorque is applied to the implant, the implant may become damaged. Suchdamage may take various forms. For example, the coating that is appliedto the surface of the implant and that is important for enhancing bonegrowth may be scrapped off the implant or otherwise damaged.Furthermore, with increasing torque, the end of the implant thatreceives the applied torque may become damaged, much the way the head ofa screw or bolt becomes stripped or rounded off. Finally, it is possiblethat the implant would fracture with excessive torque applied. In eachinstance, such damage typically would necessitate removal of the damagedimplant, thereby lengthening the time required for the surgicalprocedure and, potentially, increasing the discomfort to the patient.

[0011] Further, with excessive torque applied to the top or driven endof the implant via the drive tool and fixture mount, the damage to theend of the implant may be such that it becomes impossible to simply backthe implant out of the osteotomy using the drive tool and the fixturemount. This can further complicate the surgical procedure. Given thatthe implant cannot simply be backed out by rotating it in the oppositedirection via the drive tool and fixture mount, other special tools andprocedures need to be employed.

[0012] Once the implant is successfully installed, the still-attachedfixture mount is in position to serve other functions. For example, byextending above the gum line as it does, the fixture mount may beemployed to shape or direct the growth of gingival tissue duringhealing. Likewise, the fixture mount may be used as an impression postso that the dental surgeon or clinician may take precise impressionsthat are then used by a dental laboratory to manufacture a properlyfitting prosthesis. Furthermore, the attached fixture mount may serve asa temporary abutment for supporting a provisional or temporaryprosthesis that may be installed at the time of the original surgery andremain in place until the permanent prosthesis has been manufactured ina dental laboratory.

[0013] For use in any of these applications, however, the fixture mountmay require certain modifications, particularly when used to support atemporary prosthesis. Such modifications may involve, for example,cutting, grinding or otherwise shaping the body of the fixture mount.Given that fixture mounts have been made typically of titanium orsimilar such metals, it has been common practice for the dental surgeonto purchase a separate component for use as the temporary abutment, onethat is easier to prepare “chair-side” or that can be sent to a dentallaboratory for the custom shaping that is necessary. In such instances,the fixture mount itself is discarded and the patient may be deprived ofthe opportunity of having a temporary prosthesis fitted at the end ofthe initial surgical procedure and must instead suffer the inconvenienceof returning for a second procedure at a time when the temporaryabutment and prosthesis can be installed. Still a third procedure isthen required after the permanent prosthesis has been fabricated and isready for installation.

[0014] Although it would be desirable for the dental surgeon himself tomodify the fixture mount “chair-side,” rather than sending the pieceoffsite to be altered or reconfigured for use as a temporary abutment,for example, the tools available to the dental surgeon typically limithis ability to shape the fixture mount. As mentioned above, conventionalfixture mounts are typically made of titanium or another very strongmetal. That factor, coupled with the very small size of the fixturemount, makes it extremely difficult for the dental surgeon to makeprecise chair-side modifications to the fixture mount.

[0015] Accordingly, given the damage that can occur to an implant ifexcessive torque is applied during implantation, it would therefore beadvantageous to employ an implant drive system that would limit thetorque or rotational force that can be applied to the implant.Preferably, the system would incorporate and could be employed with thedriving tools and implants that are presently on the market and in thecurrent inventories of dental surgeons. Preferably, the system wouldlimit the rotational force or torque applied to the implant to a valuebelow that which could damage the implant and, at the same time, providea means to withdraw the implant from the osteotomy using the same systemcomponents, rather than by having to employ additional tools or acumbersome or more complicated procedure. Further, it would beadvantageous if a drive system included a fixture mount that could bereadily revised or fashioned chair-side by the dental surgeon, such thata temporary or provisional prosthesis could be fitted and installedduring the same surgical procedure in which the implant is firstinstalled.

BRIEF SUMMARY OF PREFERRED EMBODIMENTS OF THE INVENTION

[0016] There is provided herein an apparatus and system for installingan implant into a prepared surgical site and limiting the applied torqueto prevent the implant from being damaged. The system generally includesan implant, a drive tool for supplying rotational force to the implant,and a fixture mount that is disposed between and aligned with theimplant and the drive tool, and that transmits the rotational forceapplied by the drive tool to the implant. Also disclosed is a method forinstalling the implant with the fixture mount and, thereafter, employingthe fixture mount as an impression post and abutment for a temporaryprosthesis.

[0017] According to a preferred embodiment of the invention, at leastone end of the fixture mount includes an end portion that releasablyengages the adjacent end of either the drive tool or the implant, as thecase may be, and that is adapted to receive the applied torque andtransmit it to the implant so long as the torque does not exceed apredetermined value. At torque exceeding that value, the end portiondisengages itself from the adjacent member and ceases to transmit torqueto the implant.

[0018] In certain embodiments, the end portion includes a deformablesocket or a deformable extending member that, in each instance, mateswith a correspondingly sized and configured structure of the drive toolor implant. The socket may include a single recess having a non-circularshape, such as a hexagon or other polygon, or it may include an array ofrecesses, such as an array of slots, or holes. Likewise, the extendingmember may be a single extension having a non-circular cross section, ormay be an array formed by a plurality of extensions. When thepredetermined torque is exceeded, either elastic or permanentdeformation of the part occurs. In the case of elastic deformation, thesocket or extension returns to its original configuration once the drivetool is axially displaced from the fixture mount. By then re-engagingthe tool with the fixture mount and reversing the direction of the drivetool, the fixture mount is employed to remove the implant so that theosteotomy can be further prepared. In the instance of permanentdeformation, the invention permits the dental surgeon to sever thenow-deformed end of the fixture mount and employ the remaining,non-deformed portion to remove and then reinstall the implant. Accordingto the invention, the part undergoing deformation can be either end ofthe fixture mount (or both ends) or can be the end of the drive tool.

[0019] Some embodiments of the invention also include a structure andmeans to provide a back-up or secondary torque limitation. In apreferred embodiment, the end of the fixture mount adjacent to the drivetool first disengages and limits the torque to the first predeterminedvalue. As a backup torque limiting mechanism, the end of the fixturemount adjacent the implant is adapted to disengage at a secondpredetermined torque that is greater than the first torque, but one thatis still less than that which could damage the implant. Similarly, theprimary torque limitation can occur at the interconnection between thefixture mount and the implant, with the secondary limitation beingprovided at the interconnection between the fixture mount and the drivetool. In either instance, this embodiment of the invention can thusprovide a hierarchy of torque limiting structures.

[0020] The interconnection or interface between the fixture mount andthe other system components may provide torque limitation also by meansof matingly engaging sockets and extensions having engaging surfacesthat resist relative movement until a predetermined torque is exceeded,at which time the frictional forces between the engaging surfaces areovercome such that rotation of one member no longer causes rotation ofthe matingly engaged member. When the limiting torque is reached, theparts rotate relative to one another such that torque is no longertransmitted. In certain embodiments, these structures may include anextending member having a frustoconical outer surface matingly receivedwithin a socket having a similarly sized and shaped frustoconicalrecess. Likewise, the extension and mating recess may be cylindrical inshape.

[0021] To provide certain of the advantages of the invention, it ispreferred that the material from which the fixture mount is fabricatedbe a plastic, such as a thermoset plastic or a thermoplastic. Thesematerials, in addition to facilitating the torque limitation desired ofthe present invention, also yield a fixture mount that may readily serveas an abutment for a temporary prosthesis, one that is easy to shape ormodify by a dental surgeon during the same procedure in which theimplant is installed. The fixture mount and abutment thus contemplatedby this embodiment of the invention may include longitudinal channelsand circumferential grooves on the outer surface to prevent rotation ofthe temporary prosthesis. Further the channels and grooves ensureretention of the fixture mount/abutment in the impression materials thatare typically used to transfer the position and orientation of theimplant in the mouth to a dental stone model. In this manner, thefixture mount is therefore also particularly suited for use as animpression post employed to facilitate the construction of a properlyfitting and aesthetically pleasing permanent prosthesis.

[0022] More specifically, the state of the art in implant dentistry isto place the implant, take an impression immediately after placement,and then to provide the patient with a temporary abutment and temporaryprosthesis all in the same session. This procedure minimizes the timerequired to complete the implant restoration because fabrication of thefinal or permanent prosthesis can begin based on the impression taken atthe time of surgery, and because both hard and soft tissue healing canbegin with the temporary abutment in place. Further, the patient leavesthe surgery with an aesthetically pleasing, and in many cases,functional restoration and may not be required to return to the dentaloffice until the final prosthesis has been fabricated. The plasticfixture mount of certain preferred embodiments is thus particularlysuited to perform multiple functions: to limit torque applied to theimplant during installation; to provide an impression post that suppliesimplant location and orientation to the dental laboratory; and toprovide an abutment to support a temporary prosthesis.

[0023] Accordingly, the present invention comprises a combination offeatures and advantages, which enable it to overcome various problems,deficiencies or shortcomings associated with prior devices. The variouscharacteristics described above, as well as other features of theinvention, will be readily apparent to those skilled in the art uponreading the following detailed description of the preferred embodimentsof the invention, and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] For a more detailed description of preferred embodiments of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

[0025]FIG. 1 is a cross sectional view of an implant drive system madein accordance with a preferred embodiment of the present invention.

[0026]FIG. 2 is a perspective view of the fixture mount of the drivesystem shown in FIG. 1.

[0027]FIG. 3 is an elevation view of the fixture mount shown in FIG. 2.

[0028]FIG. 4 is a cross sectional view of the fixture mount shown inFIG. 3 as taken along line 4-4.

[0029]FIG. 5 is an end view of the top or coronal end of the fixturemount shown in FIG. 3.

[0030]FIG. 6 is an end view of the bottom or implant-engaging end of thefixture mount shown in FIG. 3.

[0031] FIGS. 7-15 are each a perspective view of an alternative fixturemount of the present invention.

[0032]FIG. 16 is a perspective view of an alternative implant drivesystem of the present invention.

[0033]FIG. 17 is a perspective view, similar to FIG. 2, of anotheralternative fixture mount of the present invention.

[0034]FIG. 18 is a perspective view, similar to FIG. 17, of stillanother alternative fixture mount of the present invention.

[0035]FIG. 19 is a cross sectional view of the fixture mount of FIG. 2when employed as an abutment for a temporary, single tooth prosthesis.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0036] A torque limiting implant drive system 10 employing the featuresof the present invention is shown in FIG. 1. System 10 includes dentalimplant 12, fixture mount 14, retaining screw 16 and drive tool 18, allcoaxially aligned in use. Drive system 10 may be employed to install anyone of a variety of implants.

[0037] Implant 12 is preferably made of titanium or another strong andbiocompatible metal and includes a generally cylindrical body 22 havingexternal threads 24, tapered end 26 and coronal end 28 for mateinglyengaging with fixture mount 14. Implant 12 further includes a centralthreaded bore 30 for engaging corresponding threads of retaining screw16. Coronal end 28 of implant 12 includes upwardly extending projectionsor splines 32 that are received within and engaged by correspondingstructure formed on fixture mount 14, as described below in more detail.An implant 12 having splines 32 is described in more detail in U.S. Pat.No. 5,449,291, the entire disclosure of which is hereby incorporated byreference. Retaining screw 16 includes head 17 and upper and lowerthreads 23 a, 23 b, respectively.

[0038] Referring still to FIG. 1, drive tool 18 includes shaft 19 andhex-shaped extending portion 20. As understood in the art, shaft 19mates with a hand tool (not shown) that, upon actuation by the dentalsurgeon, rotates shaft 19 and extension 20 in a preselected directionand at a predetermined speed. Hex-shaped extension 20 provides a matinginterface with fixture mount 14 as described in more detail below, andmay include a ring or clip 15 disposed in groove 21 to provide increasedfrictional force for retaining fixture mount 14 on drive extension 20.

[0039] Referring now to FIGS. 2-6, fixture mount 14 includes a generallyelongate body 34 having axis 11, an outer surface 35, an implantengaging end 36, a drive tool engaging end 38, a central cavity 40, andflange 46 adjacent drive tool engaging end 38. The outer surface 35 ofbody 34 includes flats 42 formed longitudinally on the body, and agroove 44 formed about body 34 generally adjacent to flange 46. Groove44 provides a means for engaging a removable collar such as shown anddescribed in U.S. Pat. No. 6,086,371, the entire disclosure of which isincorporated herein by reference. Such a collar may be employed tosuspend fixture mount 14 and implant 12 within a sterile deliverycontainer. As best understood with reference to FIGS. 5 and 6, flats 42are positioned circumferentially about body 34 at locations less than180 degrees apart (their surfaces being formed at an angle a relative toone another) so as to provide body 34 with an orienting extension orlobe 43 as is useful when fixture mount 14 serves as an impression postor temporary abutment. In the embodiment shown, α is preferablyapproximately 60°. The orienting lobe 43 and flats 42 (whichalternatively may be channels) ensure that a prosthesis made fromimpressions taken of fixture mount 14 after the implant 12 is installedwill resist rotation, will be properly oriented, and will correctlymatch the position of the implant. To ensure a properly-fittingprosthesis, flange 46 provides a surface that is perpendicular withrespect to axis 11 for acting against the impression material whenfixture mount 14 serves as an impression post, and against the acrylicor other material used in fabricating a temporary prosthesis when thefixture mount serves as a temporary abutment.

[0040] As best shown in FIG. 4, central cavity 40 of fixture mount 14includes a socket 48 for mating and releasably engaging extension 20 ofdrive tool 18 (FIG. 1), a central bore 50, and a threaded bore 52.Socket 48 is co-axially aligned with and interconnects to central bore50 at shoulder 49. Bore 50 extends between socket 48 and threaded bore52, bore 50 interconnecting threaded bore 52 at shoulder 51. Bore 50 isformed to have a diameter large enough to accommodate head 17 ofretaining screw 16 (FIG. 1). Threaded bore 52 extends between implantengaging end 36 and central bore 50 and is coaxially aligned with bore50.

[0041] In fixture mount 14 shown in FIGS. 1-6, socket 48 includes bandedsegments 58, 60 each having a hex-shaped opening defined by flats 56.Bands 58, 60 are separated by an annular recess 62 having a generallycylindrical surface 63. A similar annular recess 72 with cylindricalsurface 73 is formed between band 60 shoulder 49, with recesses 62, 72having substantially the same diameter and a diameter that is greaterthan the diameter of bore 50. Flats 56 and bands 58, 60 are sized toengage corresponding flat surfaces on the hexagonal extension 20 ofdrive tool 18, socket 48 and drive tool extension 20 providing aninterconnection or joint through which torque is transferred from thedrive tool to the fixture mount.

[0042] As best shown in FIGS. 2 and 4, implant engaging end 36 offixture mount 14 includes an array of six splines 64 and a cylindricalrecess or socket 75. Recess 75 includes a recess bottom 76 and acylindrical side surface 77 and is co-axially aligned with threaded bore52. Splines 64 are disposed approximately sixty degrees apart and extendaxially from recess bottom 76 and radially from recess side surface 77.The radially innermost edges of splines 64 include threads 68 (bestshown in FIG. 2). Threads 68 engage upper threads 23 a of screw 16(FIG. 1) such that, in an assembly step prior to shipment, screw 16 iscaptured within fixture mount 14 for the convenience of the dentalclinician.

[0043] Referring again to FIGS. 2 and 6, the angularly spaced splines 64create voids between the splines, such voids referred to herein asspline receptors 70, for receiving and inter-digitating with splines 32that extend from implant 12, wherein each of the implant's splines 32 isdisposed between a pair of splines 64 in a spline receptor 70. In thismanner, recess 75 of the fixture mount and coronal end 28 of the implantform an interconnection or joint through which torque is transferredfrom the fixture mount to the implant.

[0044] Fixture mount 14 is preferably made of a plastic and, moreparticularly of a thermoset plastic or a thermoplastic. One suchsuitable material for fixture mount 14 is a polyetherimide (PEI)marketed by GE Plastics under the trade name Ultem®.

[0045] To provide torque limiting characteristics, it is desirable thatthe material from which the fixture mount is constructed be able tostretch a substantial degree before breaking. This characteristic isquantified by the elongation percentage of the material. Prior artfixture mounts were made of materials having relatively little abilityto stretch. For example, titanium alloy 6A14V has an elongationpercentage of 15. For comparison purposes, tungsten carbide has anelongation percentage of 0, high strength 4340 steel has an elongationpercentage of 2.5, aluminum alloy 7075-T6 has an elongation percentageof 12. In this embodiment of the present invention, it is desirable thatthe fixture mount be made from a material having an elongationpercentage of about 50 or above. Most preferably, the material should beselected so as to have an elongation percentage of greater than 60.

[0046] Generally, materials have two modes of deformation—elastic andplastic. The division between the two modes is referred to as the yieldpoint of the material. Below the yield point, the material deformselastically, meaning that the material will return to its original shapeafter the deforming load is removed. Above the yield point, the materialdeform plastically or permanently, meaning it will not return to itsoriginal shape and will remain at least partially deformed. Deformationin the elastic region is proportional to the elastic or Young's modulusof elasticity of a material.

[0047] Prior art fixture mounts of titanium do not have the desirablemodulus of elasticity. For example, titanium 6A14V has a modulus ofelasticity equal to about 100 GPa. Various other metals similarly have ahigh modulus of elasticity and thus lack the degree of flexibilitydesirable for the fixture mount preferred for the present invention. Itis preferred that the material for the fixture mount of the presentinvention have a modulus of elasticity that is less than 45 GPa. It ismore desirable that the material selected have a modulus of elasticityof less than 10 GPa and, still more preferably, less than 5 GPa. TheUltem® PEI referred to above as suitable for fixture mount 14 has anelongation percentage of 80 and a modulus of elasticity equal to 3.3GPa.

[0048] Various thermoset plastics and thermoplastics are suitable forthe present invention. In general terms, thermoplastics will return totheir original configuration after being stretched. By contrast, athermoset plastic provides the desired elasticity and elongation, butafter stretching, it will not return entirely to its originalunstretched configuration.

[0049] As understood by those skilled in the art, the preciseconfiguration and dimensions of the various components of fixture mount14 may vary depending upon the size of the implant to be installed andthe characteristics of the material from which the fixture mount isfabricated. Thus, as an example only, one such fixture mount suitablefor the present invention and made of Ultem® 1000 is approximately 9.78mm long and has an outer diameter of approximately 4.57 mm at flange 46and an outer diameter of approximately 4.06 mm at implant engaging end36. In this example, socket 48 has a depth of approximately 4.01 mm asmeasured from drive tool engaging end 38 to shoulder 49. Annularrecesses 62, 72 have an overall diameter of approximately 3.28 mm.Banded segments 58, 60 are approximately 0.76 mm and 1.47 mm,respectively, in length and are separated by recess 62 that isapproximately 2.03 mm in length, with recess 72 being approximately 1.01mm in length. As represented by distance “D” shown in FIG. 5, flats 56extend radially inward from recess 62 a distance that is approximately0.66 mm measured at its most distant point. Given this configuration,socket 48 will deform and cease to transmit applied torque when a torquegreater than approximately 63% of the ultimate torsion strength of thesplined titanium implant is applied to the socket. As will be understoodby those skilled in the art, in this configuration of socket 48, thepre-determined torque at which the socket will cease to transmit appliedtorque may be varied by changing the widths of bands 58, 60 and thewidth of recess 62 (which defines the separation between bands 58, 60).By varying these features, as well as through the selection of thematerial used to fabricate the fixture mount, the torque at which socket48 will deform may be precisely controlled.

[0050] The use of drive system 10 to install implant 12 is bestdescribed with reference to FIG. 1. As shown, the coronal end 28 ofimplant 12 is matingly received in the implant engaging end 36 offixture mount 14 with the splines 32 of the implant being received inspline receptors 70. Retaining screw 16 secures fixture mount 14 toimplant 12 by threadingly engaging threaded bore 52 and threads 68 onsplines 64 of the fixture mount, and the internal threads in bore 30 ofthe implant. The screw head 17 bears against annular shoulder 51 withinthe fixture mount 14. Preferably, retaining screw 16, fixture mount 14and implant 12 are pre-assembled prior to shipment to the dentalsurgeon, and are shipped within a sterile delivery container such asthat disclosed in U.S. Pat. No. 6,086,371.

[0051] After preparation of the osteotomy, the hex extension 20 of drivetool 18 is fitted within socket 48 of fixture mount 14 and the assemblyformed by fixture mount 14, implant 12 and retaining screw 16 is removedfrom its shipping container. Using the drive tool 18, the assembly iscarried to the surgical site where the tapered end 26 of the implant isplaced in the osteotomy. To install the implant, the surgeon willactuate the hand piece (or employ a manual drive) which in turn willrotate the drive tool 18. The hexagonal drive tool extension 20 engagesflats 56 of socket 48 so that the rotational force from drive tool 18 istransmitted to fixture mount 14. In turn, the same force and torque istransmitted to implant 12 by means of the interdigitations of splines 64of the fixture mount 14 and splines 32 of implant 12.

[0052] If the density of bone tissue at the surgical site matchesexpectations, the implant will be threaded into the osteotomy withoutexperiencing potentially-damaging resistive forces. However, in theevent that an excessive resistive force is encountered, the torquelimiting features of the present invention will act to protect theimplant from damage. Specifically, when the torque applied by drive tool18 to fixture mount 14 increases to a pre-determined magnitude,hexagonal bands 58, 60 will undergo elastic deformation to such anextent that the hexagonal extension 20 of drive tool 18 rotates withinfixture mount socket 48 and ceases to apply further rotation force tothe fixture mount 14 or implant 12. Essentially, the hexagonal openingsin bands 58, 60 stretch to such a degree that they can no longertransmit to the implant the rotational force. In such instance, thehexagonal extension 20 of the drive tool merely spines or rotates withinsocket 48 thereby signaling the dental surgeon that the torque requiredto completely thread the implant into the osteomony could potentiallydamage the implant. Accordingly, the surgeon will then remove thehexagonal extension 20 from the socket 48 and thereby allow the socketto return to its unstretched configuration. Thereafter, the extension isagain inserted into the socket and, with the rotation drive tool nowreversed, the implant can be backed out of the osteotomy allowing thesite to be redrilled or tapped as necessary. When so prepared, the hexextension of the drive tool is again used to deliver the implant andfixture mount to the osteotomy and to install the implant at a torquebelow that which could damage the implant.

[0053] If desired, for example as a backup or secondary torque limitingmechanism, splines 64 in implant engaging end 36 of fixture mount 14 canbe sized and configured to deform should the torque-limiting features atthe drive tool engaging end 38 fail to limit torque as designed. In thismanner, should socket 48 not deform to limit the torque applied to theimplant below a first predetermined value, and should the torque beingimparted to the implant then exceed a second pre-determined torquegreater than the first, splines 64 will deform so as to protect thesplines 32 on the coronal end of the implant from being damaged. As anexample, with a splined implant such as implant 12 shown in FIG. 1 andhaving a diameter of 3.15 mm, socket 48 will deform at a torque ofapproximately 45% of the ultimate torsion strength of the implant so asto protect implant 12. In the same example, the splines 64 in theimplant engaging end 36 of fixture mount 14 are configured to deform ona second pre-determined torque of approximately 66% of the ultimatetorsion strength of the implant. Without regard to the precise torqueselected as the first pre-determined torque limit, it is beneficial thatthe second limiting torque be between 30% and 100% greater than thefirst limiting torque, and preferably be between approximately 30%-50%percent greater than the first limiting torque.

[0054] Drive system 10 and fixture mount 14 described above thus providesignificant advantage over the prior art where torque applied to thecoronal end of the implant was not controlled or limited and where,therefore, the implant could be easily damaged and rendered unuseable.The fixture mount 14 has an additional advantage over prior titaniumparts in that it can be injection molded, providing precise andeconomical manufacturing of the part.

[0055] In addition to offering a means for torque control, thenon-metallic material preferred for the fixture mount 14 of FIGS. 1-6has the additional advantage over titanium or other conventional metalswhen the surgeon or clinician desires to employ the fixture mount foruse as a temporary abutment for a provisional or temporary prosthesis.As mentioned above, because the fixture mount is preassembled to theimplant and extends above the gingival tissue, the fixture mount canconveniently serve as an impression post and as a temporary abutment tosupport a prosthesis. When used as an impression post, an impression ofthe fixture mount 14 and the attached implant is taken immediately afterthe implant is installed using a conventional elastomeric impressionmaterial. The impression replicates the flats, channels or grooves onthe outer surface of the fixture mount so that, when an analog of theimplant and fixture mount is cast at the dental laboratory using theimpression, the position and orientation of the implant in the mouth isexactly duplicated.

[0056] For use in supporting a temporary prosthesis, it is many timesdesirable to shape or otherwise modify fixture mount 14 after theimplant has been placed and the impression taken, and to do so chairside rather than having to send the piece to an offsite dentallaboratory for revision. In the latter instance, the patient isinconvenienced by having to return to the clinician's office for asecond visit, as well as by having to do without the temporary abutmentand prosthesis in the interim. Softer materials, such as thethermoplastics or thermoset plastics preferred for the presentinvention, are easier to modify chair side than are the conventionalmetallic components. Thus, after fixture mount 14 is first employed toinstall implant 12 as previously described, screw 16 is then unthreadedfrom implant 12 so as to release fixture mount 14. The fixture mount isthen removed from engagement with the implant and shaped or otherwisemodified by the dental professional so that it is better suited to formthe core or support for a temporary prosthesis. As used herein, theterms “shape” or “shaped” when used to describe the modifications madeby the dental professional to the fixture mount to allow it to serve asan abutment for a prosthesis mean and include all processes which alterthe size and/or shape of the fixture mount, including but not limited tocutting, severing, scrapping, grinding and the like.

[0057] Referring to FIG. 19, fixture mount 14 (previously described withreference to FIGS. 1-6) has been disengaged from the installed implantand then shaped by first severing drive tool engaging end 38 (FIG. 2)and approximately 50% of the length of the fixture mount so as toshorten the piece for use as an abutment 280.

[0058] In this example, fixture mount 14 is shown severed near shoulder49 (FIG. 4) and above central bore 50 so as to form an abutment 280having implant engaging end 36 and distal end 281. The outer surface ofabutment 280 is then further shaped so as to conform to and bettersupport temporary prosthesis 279. Preferably, abutment 280 is shaped toinclude a base segment 282, an end segment 284, and a shoulder 286therebetween. Comparing abutment 280 in FIG. 19 to fixture mount 14shown in FIG. 4, it can be seen that little material is removed fromfixture mount 14 to form base segment 282. Thus, base segment 282 isonly slightly tapered so as to provide a strong supporting base forprosthesis 279. Base segment 282 has its greatest diameter at flange 283that engages and supports the terminus of prosthesis 279. End segment284 preferably includes a frustoconical outer surface 287 that istapered along its length to a greater degree than base segment 282.Depending on the particular application and the structure of theprosthesis to be supported, end segment 282 may instead include asubstantially cylindrical outer surface. In either event, it ispreferred that the portion of the base segment having the greatestdiameter be larger in diameter than the diameter of the end segment 284at any location along its length. Shoulder 286 forms a transitionsurface between base segment 282 and end segment 284 and preferablyincludes a frustoconical outer surface.

[0059] Once appropriately shaped to conform to the particular prosthesisbeing fitted, the modified fixture mount, now abutment 280, isreattached to installed implant 12 by retaining screw 16, and is thenused to support the prosthesis 279 that is made or formed about abutment280 using conventional methods. According to one such method, the toothprosthesis 279 is formed directly on the abutment 280 using an acrylicmaterial. The acrylic material bonds to the modified fixture mountbecause the plastic has an affinity for the plastic material that ispreferred for the fixture mount 14, and because it is captured by thegroove and slot geometry of the fixture mount. Alternatively, apreformed tooth prosthesis can be cemented to the abutment 280 and heldin place by the same retentive geometry. This embodiment of theinvention thus permits an implant to be installed, an impression taken,and a temporary prosthesis placed all in a single surgical setting. Asused herein, the phrase “single surgical setting” when used to describethe timing associated with performing various procedures or steps meansthat all such steps are performed during a single visit to the office ofthe dental professional, as contrasted with performing those steps overmultiple visits by the patient over various days or weeks.

[0060] Accordingly, fixture mount 14, when made of plastic, provides asingle piece that is well suited as a fixture mount with torque limitingcharacteristics, an impression transfer mechanism, and an abutment for atemporary prosthesis. This makes it particularly suited for, but notlimited to, use in the anterior of the mouth where implant diameter islimited by the narrow interdental spaces, and where the lack of a toothfor even a short time would be most noticeable.

[0061] The system 10 of the present invention may employ fixture mountsconfigured in a number of ways to provide the desired torque limitingcharacteristics. One such alternative embodiment is shown in FIG. 7. Asshown therein, fixture mount 80 comprises a generally cylindrical body82 having implant engaging end 84, drive tool engaging end 86, centralbore 87 and a tool-receiving socket 88 formed on tool engaging end 86. Aretaining screw such as the one shown in FIG. 1 is disposed in bore 87and interconnects fixture mount 80 with the implant as previouslydescribed. Socket 88 includes a pair of aligned and diametricallyopposed slots 90. The outer surface of body 82 includes longitudinalchannels 92 spaced circumferentially about the body so as to form aplurality of lobes 94 there between. One lobe 94 is larger than theothers and forms an orienting lobe 98. Body 82 also includescircumferential grooves 96. As explained previously with respect to theembodiment of FIGS. 2-6, channels 92 and the orienting lobe 98 ensurethat a prosthesis made from an impression of the fixture mount will becorrectly positioned relative to the implant, and will not rotate afterit has been installed. Grooves 96, like flange 46 in the embodiment ofFIGS. 2-6, are useful in the impression process as they provide verticalsurfaces (surfaces perpendicular to the axis of the fixture mount) foracting against the impression material. Implant engaging end 84 isconfigured so as to matingly engage the coronal end of the implant and,for a splined implant 12 such as shown in FIG. 1, for example, may beidentical to implant engaging end 36 of fixture mount 14 previouslydescribed.

[0062] To install an implant using fixture mount 80, a drive tool isused that has either a single blade that is disposed within both slots90 simultaneously, or a pair of blades, each one of which is installedin one slot 90. It is preferred that slots 90 have a depth measured inthe axial direction equal to approximately twice the length of theextending drive tool blade, such that, once the drive tool blade isinserted to the maximum depth allowed by the tool, a substantial portionof slots 90 remain unfilled. As the drive tool is rotated, the torque istransmitted from the driving tool blade to the fixture mount and, inturn, to the implant. If the pre-determined torque is exceeded, socket88 is deformed by the drive tool blade to such an extent that thefixture mount ceases to transmit the torque. The deformation may be bythe stretching of the material forming the socket, or by the tearing orshearing of socket material, or other phenomenon, although in thisembodiment, it is preferred that the socket material be selected so asto permanently deform. When this occurs, the dental surgeon withdrawsthe drive tool blade and severs the deformed portion of the socket,leaving the lower portions of slots 90 intact and available forreceiving the reinserted drive tool blade or blades. Then, after theosteotomy has been further prepared, the now-shortened fixture mount 80can be used to install the implant as previously described.

[0063]FIG. 8 shows another alternative fixture mount 110 that is similarto fixture mount 80 previously described. Fixture mount 110 includesbody 112 having an implant engaging end 114 and drive tool engaging end116. Body 112 includes longitudinal channels 122 and circumferentialgrooves 124 on its outer surface. Longitudinal channels 122 are spacedapart such that body 112 is generally cross-shaped in cross section.Although longitudinal channels 122 are shown angularly spacedapproximately 90 degrees apart, the spacing of the grooves, and theirnumbers, may be varied so as to provide an orienting lobe. Tool engagingend 116 includes a socket 118 for receiving an extending segment of thedrive tool. Socket 118 includes an array of four slots 120, with oneslot formed in each extending lobe.

[0064] Socket 118 and slots 120 are sized and configured so as toreceive correspondingly sized and shaped extensions of a drive tool. Inthis embodiment, the drive tool extension may be configured like thedrive end of a phillips head screwdriver or may be formed by fourextending tabs or splines. When the drive tool is completely insertedinto socket 118, a substantial length of slots 120 remain unfilled andextend beneath the end of the drive tool extension. In this manner, whenexcessive torque is applied to socket 118 by the drive tool, the upperend of the socket 118 deforms so that further torque cannot be applied.As with fixture mount 80 previously described, the deformed end ofimplant 110 can then be severed by the surgeon and the drive toolreinserted to drive the implant using the undeformed and remainingsections of slots 120.

[0065] Another alternative embodiment of the invention is shown in FIG.9, this embodiment being similar in many respects to the embodimentshown in FIG. 8. Referring to FIG. 9, fixture mount 130 includes body132 having a drive tool engaging end 134 with socket 136. Socket 136includes an array of six axially extending slots 138 that are sized andconfigured to matingly receive corresponding splines or tabs extendingfrom a drive tool. As previously described, the axial depth of slots 138exceeds the length of the drive tool splines and preferably areapproximately two times as long as the drive tool's extensions. Body 132includes longitudinal channels 133 spaced so as to form lobes 135,including and an orienting lobe 137.

[0066] Another alternative embodiment of the fixture mount of presentinvention is shown in FIG. 10 wherein fixture mount 140 includes asocket 142 on drive tool engaging end 144. Socket 142 includes an arrayof six parallel bores 148 for receiving similarly configured cylindricalextensions of the drive tool. As previously described, the axial lengthor depth of bores 148 will be approximately twice the length of thecylindrical extensions so that, when a pre-determined maximum torque isapplied to the fixture mount 140, the drive tool engaging end of thefixture mount will be deformed. However, by removing the deformedsection of the fixture mount 140, the remaining length of the bores 148may be used to install the implant using the fixture mount 140 and thedrive tool.

[0067] Heretofore, the drive tool engaging end of the fixture mount hasbeen shown and described as having a socket comprising one or morepolygonal openings, slots, or bores for receiving a correspondinglyconfigured extension on the drive tool. Similarly, the fixture mount maybe constructed such that the drive tool engaging end has one or moreextensions that are sized and shaped so as to engage a correspondinglyconfigured socket or receptacle in a drive tool. For example, referringto FIG. 11, a fixture mount 150 is shown having drive tool engaging end152 including hexagonal extension 154. Hex extension 154 includes flats155 intersecting at corners or edges 156. A drive tool to be employedwith fixture mount 150 includes a hexagonal shaped socket sized toreceive hex extension 154. Torque limiting with fixture mount 150 iscontrolled through the selection of appropriate material and the shapeand size of the polygonal extension 154. In the embodiment shown in FIG.11, when an excess torque is applied, the corners 156 of the polygonalextension will deform such that further rotation of the drive tool doesnot rotate the fixture mount or the attached implant. The fixture mount150 includes one or more flats 158 formed about its length so as toprovide for orientation and anti-rotation.

[0068] Another alternative embodiment of the invention is shown in FIG.12. As shown, fixture mount 160 is similarly structured to theembodiment shown in FIG. 9. Rather than including a slotted socket,however, fixture mount 160 includes six extending tabs or splines 162sized and configured to mate with a socket in a drive tool having sixcorrespondingly sized and oriented slots for receiving the tabs. In thisembodiment, when an excessive torque is applied to fixture mount 160,tabs 162 bend or otherwise deform so that the excessive torque cannot beapplied and damage to the implant can be prevented.

[0069] In addition to providing the desired torque control by means ofthe interconnections previously described, the torque applied by thedrive tool may likewise be limited by employing matingly engagingcomponents that rely on the frictional force between opposing surfacesto transfer the applied torque up until such time as the pre-determinedmaximum torque is reached. When excessive torque is applied, thefrictional forces are overcome and the mating surfaces slide against oneanother, thereby preventing excessive torque from being applied to theimplant.

[0070] For example, referring to FIG. 13, an alternative embodiment ofthe present invention is shown and includes a fixture mount 170 havingbody 172, and a socket 176 on drive tool engaging end 174. Socket 176has a nonplanar, frustoconical inner surface 171, and is widest at itsterminal end 177 and narrowest at its inner end 178. The externalsurface of body 173 includes a pair of flat surfaces 175 angularlyspaced approximately 60 degrees apart so as to provide an orienting lobe179. Fixture mount 170 is to be employed with a drive tool extensionhaving an outer surface having a corresponding frustoconical shape ofsubstantially the same taper as socket 176. In use, the frustoconicaldrive end of the drive tool is inserted into socket 176 and a constantaxial force is applied to the fixture mount by the drive tool.

[0071] The materials for fixture mount 170 and the depth and degree oftaper of socket 176 are chosen so that the torque control can beprovided by controlling the frictional forces between the driveextension and socket 176. More specifically, the materials and size andshape of the socket are configured and selected such that at a torqueless than the predetermined limiting torque, the friction between theopposing surface of socket 175 and the drive tool extension transmit theapplied torque and prevent relative motion between the opposingsurfaces. However, when the torque applied exceeds the pre-determinedlimit, the rotational force overcomes the frictional forces between thetwo elements such that the drive tool extension will slip and rotatewithin socket 176 and transmit no further rotational force such thatdamaging torque will not be applied.

[0072] Referring now to FIG. 14, a fixture mount 180 similar to thatdescribed with reference to FIG. 13 is shown and includes body 182 and afrustoconical extension 184 of a given taper and length. Fixture mount180 is intended to be employed with a drive tool having a similarlyshaped and sized frustoconical socket. Like the embodiment FIG. 13,before a predetermined maximum torque is reached, the friction betweenthe drive tool socket and the frustoconical extension 184 of the fixturemount 180 will impart rotational force to the fixture mount and thus tothe implant. When an excessive torque is required to further drive theimplant, the socket end of the drive tool will begin to slide about theextension 184 to prevent further rotational of fixture mount 180 and theattached implant.

[0073] Still a further embodiment of the invention is shown in FIG. 15wherein a fixture mount 190 includes body 192 and a cylindricalextension 194, rather than one having a frustoconical surface such aspreviously described with reference to FIG. 14. Fixture mount 190 is tobe employed with a drive tool having a cylindrical socket. The outerdiameter of extension 194 and the internal diameter of the drive toolsocket are closely matched such that a friction fit is created. Thefriction allows the drive tool to impart a rotational force to thefixture mount 190 until such time as an excessive resistive force isencountered. When a predetermined maximum torque is reached, the drivetool socket slips about extension 194 of the fixture mount 190 andimparts no further rotational force or torque.

[0074] Another embodiment of the present invention is shown in FIG. 16which, as with the embodiments of FIGS. 13-15 previously described,relies on the frictional forces of opposing but non-interlockingsurfaces to apply only limited torque to the fixture mount. As shown inFIG. 16, fixture mount 200 includes a general cylindrical body 202having a drive tool engaging end 204 and an implant engaging end 206that terminates in a generally flat annual surface 208. Implant 250 issubstantially the same as implant 12 previously described and includes asubstantially, flat annular surface 13 at its coronal end betweensplines 32 and the outermost surface of the implant for engaging annularsurface 208 of the fixture mount. As with the embodiment shown in FIG.1, a retaining screw 210 bears against an internal ledge in fixturemount 200 and is threaded into a central bore of the implant 250 therebydrawing together fixture mount 200 and implant 250. When fixture mount200 and implant 250 are interconnected, surface 208 of the fixture mountabuts the corresponding surface 13 on the coronal end of the implant.The drive tool engaging end 204 of fixture mount 200 may have any of themating engagements previously described so as to interface with a drivetool. In this embodiment, the desired torque limiting is achieved byemploying the frictional forces between annular surface 208 of thefixture mount and surface 13 on the implant's coronal end, and betweenthe head 17 of the retaining screw and internal shoulder 51 of thefixture mount (FIG. 1). Depending upon the materials selected for thefixture mount and the implant 250, the size of surfaces 208 and 13, andthe force applied by the retaining screw 210, the torque applied by thedrive tool to the fixture mount 200 is transferred to the implant 250until such time a predetermined excessive torque is reached, at whichtime annular surfaces 208 and 13 slip against one another as thefrictional forces between them are overcome by the resistive forceimparted to the implant.

[0075] As previously explained, the present invention may be used withimplants having a variety of designs. For example, a number ofconventional implants are constructed so as to have either a polygonalextension or a polygonal socket at the coronal end of the implant. Theprinciples of the present invention can be applied so as to create adrive system and fixture mount for limiting the torque that is appliedto such implants. More specifically, referring to FIG. 17, there isshown a fixture mount 220 substantially similar to fixture mount 14previously described; however, fixture mount 220 does not includesplines 64 and spline receptors 70 but instead includes a hexagonalsocket 222 at its implant engaging end 224. Socket 222 is sized andconfigured to matingly receive a correspondingly sized and shapedhexagonal projection on the coronal end of an implant. The drive toolengaging end 226 of fixture mount 220 may be configured like any of theembodiments previously described, or in an equivalent way. Torquelimitation is provided by socket 222 such that, when a pre-determinedtorque is reached socket 222 will deform and spin about the hexagonalextension of the implant so as to prevent further torque from beingapplied to the implant.

[0076] Another alternative for providing torque limitation at theimplant, engaging end of a fixture mount is shown in FIG. 18. As shown,the fixture mount 240 includes an implant engaging end 242 having ahexagonal extension 244 sized and shaped so as to be received within acorresponding hexagonal recess or socket in the coronal end of animplant. As described with respect to FIG. 17, should a predeterminedtorque be exceeded, the extension 244 on the implant engaging end 242 ofthe fixture mount will deform and spin within the socket of the implant260 so as to prevent damaging torque from being applied to the implant.

[0077] For any of the embodiments described herein, the fixture mountmay be designed to limit applied torque at either the tool engaging endor the implant engaging end or both. Where the fixture mount employstorque limiting features at each end, either end can be configured toprovide the first or primary torque control when a first predeterminedtorque is applied, with the opposite end operating as a backup mechanismto limit applied torque to a second predetermined torque that is greaterthan the first predetermined limiting torque should the primary torquelimiting structures fail to deform or otherwise operate as intended.Injection molding is the currently-preferred method of manufacturing allof the fixture mounts disclosed herein, and it is believed beneficial tomanufacture the entire fixture mount of the same material; however, ifdesired, the end portions of the fixture mount may be made of adifferent material than the central portion of the fixture mount body.

[0078] Various exemplary structures have been described herein forallowing the fixture mount to releasably engage the adjacent end of adrive tool or implant in an interconnection that provides the desiredtorque limiting characteristics. In each instance, the interconnectionemploys an extending portion from one part that is received within arecess in the other. It should be understood that the extensions andrecesses can be one or many, and that they may be constructed in amyriad of sizes, shapes and configurations. Accordingly, as used herein,the term “mating element” shall broadly mean any type of extendingelement or array of extensions for matingly engaging a recess or socketin an adjacent and aligned part, or any type of recess or socket thatmatingly receives an extending element or elements from an adjacent andaligned part, where the pair of elements releasably mate to form atorque-transmitting joint. The term “corresponding mating element” meansand refers to a mating element on one part that is sized and configuredto mate with its counterpart element from an opposing part and form atorque-transmitting joint. A hexagonal shaped recess, for example, is acorresponding mating element to an extension having a similarly sizedand shaped hexagonal extension. Similarly, an array of extending splinesis a corresponding mating element to a socket having an array ofrecesses that are sized and spaced so as to matingly receive thesplines.

[0079] As previously explained, providing a means for limiting thetorque that is applied to an implant during installation is achieved byappropriately configuring the aligned components and through theselection of materials for those components. Although plastic is thepreferred material for the fixture mounts specifically described, thefixture mount may be made of metal as well. For example, the fixturemounts shown in FIGS. 2-12 could be made of titanium and provide thedesirable torque limitation provided the walls of the socket (or thediameter of projecting members) were made relatively thin. Soconfigured, the walls of the socket or the projections would permanentlydeform upon application of a predetermined torque, at which point thedrive tool would rotate without transmitting further torque. The metalfixture mount, however, would not have the advantage of being easilymodified chair-side for use as a temporary abutment for supporting atemporary prosthesis. Further, permanent deformation of a metal fixturemount might make it impossible to use the fixture mount to remove apartially-installed implant.

[0080] While preferred embodiments of this invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit or teaching of this invention. Theembodiments described herein are exemplary only and are not limiting.Many variations and modifications of the system, apparatus and methodsare possible and are within the scope of the inventions claimed below.Accordingly, the scope of protection is not limited to the embodimentsdescribed herein, but is only limited by the claims which follow, thescope of which shall include all equivalents of the subject matter ofthe claims.

What is claimed is:
 1. An abutment for attachment to a dental implantand for supporting a prosthesis on the implant, said abutmentcomprising: an elongate body entirely made of plastic and having alongitudinal axis, an outer surface, a base segment for engaging theimplant, an end segment for engaging the prosthesis, and a central borefor receiving a retaining screw attaching said abutment to the implant;and wherein the end segment is adapted to engage a driving tool thattransmits torque to the abutment to drive the dental implant into bone.2. The abutment of claim 1 wherein the central bore at the end segmentincludes a socket adapted to engage the driving tool and transmit torquethrough the body to the implant.
 3. The abutment of claim 2 wherein saidouter surface is adapted to receive impression material and includes atleast one flat section.
 4. The abutment of claim 3 wherein said bodyincludes an orienting lobe.
 5. The abutment of 3 wherein said body isformed from a thermoplastic adapted to be shaped.
 6. The abutment ofclaim 5 wherein said base segment has a diameter larger than thediameter of said end segment.
 7. The abutment of claim 6 wherein saidbody includes an outer shoulder between said base segment and said endsegment.
 8. The abutment of claim 6 wherein said body is made of amaterial having an elongation percentage greater than 50% and a modulusof elasticity less than 45 Gpa.
 9. An abutment for supporting a dentalprosthesis on an implant, said abutment comprising: a body made of amaterial having an elongation percentage greater than 50% and a modulusof elasticity less than 45 Gpa, said body having a base segment forengaging the implant, and a distal end segment of a given lengthopposite said base segment for engaging the prosthesis; wherein said endsegment, at each location along its length, is smaller in diameter thanthe diameter of said base segment at its greatest diameter.
 10. Theabutment of claim 9 further comprising a mating element on said basesegment for mateingly engaging the implant and transmitting torque tothe implant when said abutment body is rotated.
 11. A method forproviding a dental restoration in a patient's mouth, the methodcomprising the steps of: (a) creating a bore in the patient's alveolar;(b) installing a dental implant into said bore using a plastic fixturemount that engages the coronal end of said implant and transmits to saidimplant torque that is supplied by a drive tool; (c) disengaging thefixture mount from the installed implant and removing said fixture mountfrom the patient's mouth; (d) shaping said fixture mount into anabutment for supporting a prosthesis; (e) reattaching said shapedfixture mount to the coronal end of said implant; (f) attaching aprosthesis to said shaped fixture mount.
 12. The method of claim 11wherein at least steps (b) through (f) are performed during a singlesurgical setting.
 13. The method of claim 11 wherein all steps (a)through (f) are performed during a single surgical setting.
 14. Themethod of claim 12 wherein step (f) includes: applying an acrylicmaterial to said shaped fixture mount; allowing said acrylic material toharden; and shaping said hardened acrylic material to form theprosthesis.
 15. The method of claim 11 further comprising the step ofmaking an impression of said fixture mount on said implant at a timebefore said prosthesis is attached to said shaped fixture mount.
 16. Themethod of claim 11 wherein step (d) includes severing a length of saidfixture mount.
 17. The method of claim 11 wherein step (d) includesshaping said fixture mount into an abutment having a base segment forengaging the implant and an end segment opposite said base segment thatis smaller in diameter than the diameter of the base segment.
 18. Themethod of claim 11 wherein step (d) includes shaping said fixture mountinto an abutment having an end segment that includes a frustoconicalouter surface.
 19. A method for attaching a dental prosthesis to animplant that is affixed in a patient's mouth, the method comprising thesteps of: (a) attaching to the implant an elongate body that is formedof a material having an elongation percentage greater than 50% and amodulus of elasticity less than 45 Gpa; (b) making an impression of thebody attached to the implant; (c) disengaging the body from the implantand removing the body from the patient's mouth; (d) shaping said body;(e) reattaching the now-shaped body to the implant; (f) attaching aprosthesis to the shaped body.
 20. The method of claim 19 wherein allsteps (a) through (f) are performed during a single surgical setting.21. The method of claim 20 wherein step (f) includes: applying anunhardened material to said shaped body and allowing the material toharden; and shaping the hardened material to form the prosthesis. 22.The method of claim 19 wherein step (d) includes severing a length ofsaid body.
 23. The method of claim 19 wherein step (d) includes shapingsaid body into an abutment having a base segment for engaging theimplant and an end segment opposite said base segment that is smaller indiameter than the diameter of the base segment.
 24. The method of claim19 wherein step (d) includes shaping said body into an abutment havingan end segment that includes a frustoconical outer surface.